Proximity switch assembly and method having adaptive time delay

ABSTRACT

A proximity switch assembly and method for detecting activation of the proximity switch assembly is provided. The assembly includes a plurality of proximity switches each providing a sense activation field and control circuitry processing the activation field of each proximity switch to sense activation. The control circuitry monitors the signal responsive to the activation field, determines a rate of change in signal amplitude for each signal, and generates an adaptive time delay based on the control circuitry. The control circuitry further detects a peak amplitude of the signal and determines activation of the switch after expiration of the time delay following the peak amplitude detection.

FIELD OF THE INVENTION

The present invention generally relates to switches, and more particularly relates to proximity switches having an adaptive determination of switch activation.

BACKGROUND OF THE INVENTION

Automotive vehicles are typically equipped with various user actuatable switches, such as switches for operating devices including powered windows, headlights, windshield wipers, moonroofs or sunroofs, interior lighting, radio and infotainment devices, and various other devices. Generally, these types of switches need to be actuated by a user in order to activate or deactivate a device or perform some type of control function. Proximity switches, such as capacitive switches, employ one or more proximity sensors to generate a sense activation field and sense changes to the activation field indicative of user actuation of the switch, typically caused by a user's finger in close proximity or contact with the sensor. Capacitive switches are typically configured to detect user actuation of the switch based on comparison of the sense activation field to a threshold.

Switch assemblies often employ a plurality of capacitive switches in close proximity to one another and generally require that a user select a single desired capacitive switch to perform the intended operation. In some applications, such as use in an automobile, the driver of the vehicle has limited ability to view the switches due to driver distraction. In such applications, it is desirable to allow the user to explore the switch assembly for a specific button while avoiding a premature determination of switch activation. Thus, it is desirable to discriminate whether the user intends to activate a switch, or is simply exploring for a specific switch button while focusing on a higher priority task, such as driving, or has no intent to activate a switch. Accordingly, it is desirable to provide for a proximity switch arrangement which enhances the use of proximity switches by a person, such as a driver in a vehicle.

SUMMARY OF THE INVENTION

According to one aspect of the present invention, a method for detecting activation of a proximity switch is provided. The method includes the steps of generating an activation field with a proximity sensor and monitoring a signal responsive to the activation field. The method also includes the step of generating an adaptive time delay based on a rate of change of the monitored signal. The method further includes the steps of detecting a peak amplitude of the signal and determining activation of the switch after expiration of the time delay following the peak amplitude detection.

According to another aspect of the present invention, a method for detecting activation of a proximity switch is provided. The method includes the steps of generating activation fields with a plurality of proximity sensors associated with a plurality of proximity switches and monitoring a signal responsive to each of the activation fields. The method also includes the steps of determining a rate of change in signal amplitude for each signal and generating an adaptive time delay based on the rate of change. The method further includes the steps of detecting a peak amplitude of the signal and determining activation of one of the proximity switches after expiration of the time delay following the peak amplitude detection.

According to a further aspect of the present invention, a proximity switch assembly is provided. The proximity switch assembly includes a plurality of proximity switches each providing a sense activation field. The proximity switch also includes control circuitry processing the activation field of each proximity switch to sense activation. The control circuitry monitors a signal responsive to the activation field, generates a rate of change in signal amplitude, detects a peak amplitude of the signal, and determines activation of a switch after expiration of the adaptive time delay following the peak amplitude detection.

These and other aspects, objects, and features of the present invention will be understood and appreciated by those skilled in the art upon studying the following specification, claims, and appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a perspective view of a passenger compartment of an automotive vehicle having an overhead console employing a proximity switch assembly, according to one embodiment;

FIG. 2 is an enlarged view of the overhead console and proximity switch assembly shown in FIG. 1;

FIG. 3 is an enlarged cross-sectional view taken through line III-III in FIG. 2 showing an array of proximity switches in relation to a user's finger;

FIG. 4 is a schematic diagram of a capacitive sensor employed in each of the capacitive switches shown in FIG. 3;

FIG. 5 is a graph illustrating the signal count for three channels associated with the capacitive sensors illustrating in FIG. 3 as a user slides a finger across the switch assembly;

FIG. 6 is a block diagram illustrating the proximity switch assembly, according to one embodiment; and

FIG. 7 is a flow diagram illustrating a routine for providing an adaptive-time delay for determining activation of the proximity switches, according to one embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to a detailed design; some schematics may be exaggerated or minimized to show function overview. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.

Referring to FIGS. 1 and 2, the interior of an automotive vehicle 10 is generally illustrated having a passenger compartment and a switch assembly 20 employing a plurality of proximity switches 22 having an adaptive time determination, according to one embodiment. The vehicle 10 generally includes an overhead console 12 assembled to the headliner on the underside of the roof or ceiling at the top of the vehicle passenger compartment, generally above the front passenger seating area. The switch assembly 20 has a plurality of proximity switches 22 arranged close to one another in the overhead console 12, according to one embodiment. The various proximity switches 22 may control any of a number of vehicle devices and functions, such as controlling movement of a sunroof or moonroof 16, controlling movement of a moonroof shade 18, controlling activation of one or more lighting devices such as interior map/reading and dome lights 30, and various other devices and functions. However, it should be appreciated that the proximity switches 22 may be located elsewhere on the vehicle 10, such as in the dash panel, on other consoles such as a center console, integrated into a touch screen display 14 for a radio or infotainment system such as a navigation and/or audio display, or located elsewhere onboard the vehicle 10 according to various vehicle applications.

The proximity switches 22 are shown and described herein as capacitive switches, according to one embodiment. Each proximity switch 22 includes at least one proximity sensor that provides a sense activation field to sense contact or close proximity (e.g., within one millimeter) of a user in relation to the one or more proximity sensors, such as a swiping motion by a user's finger. Thus, the sense activation field of each proximity switch 22 is a capacitive field in the exemplary embodiment and the user's finger has electrical conductivity and dielectric properties that cause a change or disturbance in the sense activation field as should be evident to those skilled in the art. However, it should also be appreciated by those skilled in the art that additional or alternative types of proximity sensors can be used, such as, but not limited to, inductive sensors, optical sensors, temperatures sensors, resistive sensors, the like, or a combination thereof. Exemplary proximity sensors are described in the Apr. 9, 2009, ATMEL® Touch Sensors Design Guide, 10620 D-AT42-04/09, the entire reference hereby being incorporated herein by reference.

The proximity switches 22 shown in FIGS. 1 and 2 each provide control of a vehicle component or device or provide a designated control function. One or more of the proximity switches 22 may be dedicated to controlling movement of a sunroof or moonroof 16 so as to cause the moonroof 16 to move in an open or closed direction, tilt the moonroof, or stop movement of the moonroof based upon a control algorithm. One or more other proximity switches 22 may be dedicated to controlling movement of a moonroof shade 18 between open and closed positions. Each of the moonroof 16 and shade 18 may be actuated by an electric motor in response to actuation of the corresponding proximity switch 22. Other proximity switches 22 may be dedicated to controlling other devices, such as turning an interior map/reading light 30 on, turning an interior map/reading light 30 off, turning a dome lamp on or off, unlocking a trunk, opening a rear hatch, or defeating a door light switch. Additional controls via the proximity switches 22 may include actuating door power windows up and down. Various other vehicle controls may be controlled by way of the proximity switches 22 described herein.

Referring to FIG. 3, a portion of the proximity switch assembly 20 is illustrated having an array of three serially arranged proximity switches 22 in close relation to one another in relation to a user's finger 34 during use of the switch assembly 20. Each proximity switch 22 includes one or more proximity sensors 24 for generating a sense activation field. According to one embodiment, each of the proximity sensors 24 may be formed by printing conductive ink onto the top surface of the polymeric overhead console 12. One example of a printed ink proximity sensor 24 is shown in FIG. 4 generally having a drive electrode 26 and a receive electrode 28 each having interdigitated fingers for generating a capacitive field 32. It should be appreciated that each of the proximity sensors 24 may be otherwise formed such as by assembling a preformed conductive circuit trace onto a substrate according to other embodiments. The drive electrode 26 receives square wave drive pulses applied at voltage V_(I). The receive electrode 28 has an output for generating an output voltage V_(O). It should be appreciated that the electrodes 26 and 28 may be arranged in various other configurations for generating the capacitive field as the activation field 32.

In the embodiment shown and described herein, the drive electrode 26 of each proximity sensor 24 is applied with voltage input V_(I) as square wave pulses having a charge pulse cycle sufficient to charge the receive electrode 28 to a desired voltage. The receive electrode 28 thereby serve as a measurement electrode. In the embodiment shown, adjacent sense activation fields 32 generated by adjacent proximity switches 22 overlap slightly, however, overlap may not exist according to other embodiments. When a user or operator, such as the user's finger 34, enters an activation field 32, the proximity switch assembly 20 detects the disturbance caused by the finger 34 to the activation field 32 and determines whether the disturbance is sufficient to activate the corresponding proximity switch 22. The disturbance of the activation field is detected by processing the charge pulse signal associated with the corresponding signal channel. When the user's finger 34 contacts two activation fields 32, the proximity switch assembly 20 detects the disturbance of both contacted activation fields 32 via separate signal channels. Each proximity switch 22 has its own dedicated signal channel generating charge pulse counts which is processed as discussed herein.

Referring to FIG. 5, the change in sensor charge pulse counts shown as Δ Sensor Count for a plurality of signal channels associated with a plurality of proximity switches 22, such as the three switches 22 shown in FIG. 3 is illustrated, according to one example. The change in sensor charge pulse count is the difference between an initialized referenced count value without any finger or other object present and the corresponding sensor reading. In this example, the user's finger enters the activation fields 32 associated with each of three proximity switches 22, generally one sense activation field at a time with overlap between adjacent activation fields 32 as the user moves across the array of switches. Channel 1 is the change in sensor charge pulse count associated with a first capacitive sensor 24, channel 2 is the change in sensor charge pulse count associated with the next adjacent capacitive sensor 24, and channel 3 is the change in sensor charge pulse count associated with the third capacitive sensor 24. In the disclosed embodiment, the proximity sensors 24 are capacitive sensors. When a user's finger is in contact or close proximity of a sensor 24, the finger alters the capacitance measured at the corresponding sensor 24. The capacitance is in parallel to the untouched sensor pad parasitic capacitance, and as such, measures as an offset. The user or operator induced capacitance is proportional to the user's finger or other body part dielectric constant, the surface exposed to the capacitive pad, and is inversely proportional to the distance of the user's limb to the switch button. According to one embodiment, each sensor is excited with a train of voltage pulses via pulse width modulation (PWM) electronics until the sensor is charged up to a set voltage potential. Such an acquisition method charges the receive electrode 28 to a known voltage potential. The cycle is repeated until the voltage across the measurement capacitor reaches a predetermined voltage. Placing a user's finger on the touch surface of the switch 24 introduces external capacitance that increases the amount of charge transferred each cycle, thereby reducing the total number of cycles required for the measurement capacitance to reach the predetermined voltage. The user's finger causes the change in sensor charge pulse count to increase since this value is based on the initialized reference count minus the sensor reading.

The proximity switch assembly 20 is able to recognize the user's hand motion when in close proximity to the proximity switches 24, to discriminate whether the intent of the user is to activate a switch 24, explore for a specific switch button while focusing on higher priority tasks, such as driving, or is the result of a task such as adjusting the rearview mirror that has nothing to do with actuation of a proximity switch 24. The proximity switch assembly 20 may operate in an exploration or hunting mode which enables the user to explore the keypads or buttons by passing a finger in close proximity to the switches without triggering an activation of a switch until the user's intent is determined. The proximity switch assembly 20 advantageously generates an adaptive time delay based on a rate of change of the monitored signal and determines activation of the proximity switch after expiration of the time delay following detection of a peak signal amplitude. The adaptive time delay may vary such that as the operator moves the finger fast, activation decisions are determined quickly, whereas if the operator moves the finger slower, the determination of activation slows down. As a result, exploration of the proximity switch assembly 20 is allowed with reduced inadvertent switch activations.

As the user's finger 34 approaches a switch 24, the finger 34 enters the activation field 32 associated with the switch 24 which causes disruption to the capacitance thereby resulting in a sensor count increase as shown in FIG. 5. For the signal on channel 1, the sensor count increases as the capacitance disturbance increases until a peak value at point 38 is detected. As the sensor count rises for signal channel 1, the signal reaches a first active threshold at point 36. The proximity switch assembly 20 determines an adaptive time period ΔT for the signal to increase from the first or active threshold C_(A) at point 36 to the second or peak threshold at point 38 shown represented as ΔT. The adaptive time ΔT is then used as a time delay for determining activation of the proximity switch following the peak amplitude detection. Accordingly, when a peak amplitude is detected at point 38, the timer times down to zero so as to expire before making a decision as to whether or not an activation of the proximity switch has been detected. If the signal drops below the count threshold C_(T) prior to the adaptive time delay expiring, no switch activation is detected. In the example shown in FIG. 5, the signal on channel 1 drops below the count threshold C_(T) prior to the adaptive time ΔT expiring following the peak point 38. Thus, no activation of the first proximity switch is determined.

The signal at channel 2 associated with the next adjacent switch is shown rising up to a threshold greater than the signal of the first channel. The second signal channel is shown rising to a peak value at point 38. In doing so, an adaptive time delay ΔT is generated from the time that the signal on the second channel rises from the first or active threshold C_(A) at point 36 to the second or peak threshold at point 38. The adaptive time delay ΔT for the second channel is then used as an expiration time following detection of the peak signal at point 38.

In this example, the second signal decreases from its peak at point 38 down below the count threshold C_(T) and thereafter the signal on the third channel associated with the next adjacent proximity switch rises up and becomes the maximum amplitude signal. An adaptive time delay ΔT is generated for the third channel from the point in time in which the third channel signal rises from the first or active threshold C_(A) at point 36 to the second or peak threshold at point 38. The adaptive time period ΔT is allowed to expire before determining whether the third signal channel has an amplitude that exceeds the count threshold C_(T) which occurs at point 50. Since the adaptive time period ΔT has expired and the third signal channel exceeds the count threshold C_(T), a determination as to activation of the third switch is made at point 50.

The proximity switch assembly 20 allows a user to explore the switch keypads by delaying the decision to activate a switch based on the adaptive time ΔT. The proximity switch assembly 20 determines activation of a switch when the count signal for the highest signal channel exceeds the count threshold C_(T) after expiration of adaptive time ΔT following the peak signal detection. As shown, the adaptive time period ΔT changes based on the rising slope of the signal of the corresponding proximity switch. Accordingly, as a user moves the finger faster, the activation decisions are increased, and as the user moves the finger slower, the activation decisions are slowed down due to the adaptive time delay.

To make a determination of a clean switch activation, there should be only one triggering event. To improve robustness, hysteresis may be provided in the determination of the peak signal. For a count reading at the peak signal to be recognized as the peak amplitude, the signal must be lower than the peak minus the level of electrical noise for a set amount of time, such as 100 milliseconds. This waiting period may be subtracted from the adaptive time delay ΔT if a more responsive system is desired. If, on the other hand, an enhanced robustness is desired, an additional delay can be added to the adaptive time ΔT. The added time delay may depend upon the distance between sensors and may be for 100 milliseconds according to one example to provide added noise reduction.

Referring to FIG. 6, the proximity switch assembly 20 is illustrated according to one embodiment. A plurality of proximity sensors 24 are shown providing inputs to a controller 40, such as a microcontroller. The controller 40 may include control circuitry, such as a microprocessor 42 and memory 48. The control circuitry may include sense control circuitry processing the activation field of each sensor 22 to sense user activation of the corresponding switch by comparing the activation field to a threshold pursuant to the adaptive time determination routine. It should be appreciated that other analog and/or digital control circuitry may be employed to process the activation field, determine user activation, and initiate an action. The controller 40 may employ a QMatrix acquisition method available by ATMEL®, according to one embodiment. The ATMEL acquisition method employs a WINDOWS® host C/C++ compiler and debugger WinAVR to simplify development and testing the utility Hawkeye that allows monitoring in real-time the internal state of critical variables in the software as well as collecting logs of data for post-processing.

The controller 40 provides an output signal to one or more devices that are configured to perform dedicated actions responsive to correct activation of a proximity switch. For example, the one or more devices may include a moonroof 16 having a motor to move the moonroof panel between open and closed and tilt positions, a moonroof shade 18 that moves between open and closed positions, and lighting devices 30 that may be turned on and off. Other devices may be controlled such as a radio for performing on and off functions, volume control, scanning, and other types of devices for performing other dedicated functions. One of the proximity switches 22 may be dedicated to actuating the moonroof closed, another proximity switch 22 may be dedicated to actuating the moonroof open, and a further switch 22 may be dedicated to actuating the moonroof to a tilt position, all of which would cause a motor to move the moonroof to a desired position. The moonroof shade 18 may be opened in response to one proximity switch 22 and may be closed responsive to another proximity switch 22.

The controller 40 is further shown having an analog to digital (A/D) comparator 44 coupled to the microprocessor 42. The A/D comparator 44 receives the voltage output V_(O) from each of the proximity switches 22, converts the analog signal to a digital signal, and provides the digital signal to the microprocessor 42. Additionally, controller 40 includes a pulse counter 46 coupled to the microprocessor 42. The pulse counter 46 counts the charge signal pulses that are applied to each drive electrode of each proximity sensor, performs a count of the pulses needed to charge the capacitor until the voltage output V_(O) reaches a predetermined voltage, and provides the count to the microprocessor 42. The pulse count is indicative of the change in capacitance of the corresponding capacitive sensor. The controller 40 is further shown communicating with a pulse width modulated drive buffer 60. The controller 40 provides a pulse width modulated signal to the pulse width modulated drive buffer 60 to generate a square wave pulse train V_(I) which is applied to each drive electrode of each proximity sensor. The controller 40 processes a control routine 100 stored in memory to determine the adaptive time period and to make a determination as to activation of one of the proximity switches based upon the adaptive time period.

Referring to FIG. 7, the adaptive time determination control routine 100 is illustrated according to one embodiment. Routine 100 begins at step 102 and proceeds to step 104 to find the maximum signal channel, a sum channel which is the sum of all signal channels, and the number of active channels greater than a threshold. Next, at decision step 106, routine 100 determines if the switch active is equal to no switch indicative of no active switches and, if not, proceeds to decision step 108 to determine if the maximum channel is less than the active threshold. If the maximum channel is less than the active threshold, routine 100 proceeds to set the switch active equal to no switch at step 110 before proceeding to step 132. If the maximum channel is not less than the active threshold, then routine 100 proceeds to step 132.

Returning back to decision step 106, if the switch active is not equal to no switch, then routine 100 proceeds to decision step 112 to determine if the maximum channel is greater than the active threshold and, if not, proceeds to step 132. If the maximum channel is greater than the active threshold, routine 100 proceeds to decision step 114 to determine if a new maximum channel exists and, if so, resets the peak reached flag and resets the timer to peak at step 116. Next, at decision step 118, routine 100 determines if the peak reached flag is set equal to true and, if not, proceeds to step 120 to determine if the peak has been reached. If the peak has been reached, routine 100 proceeds to step 122 to set the peak reached flag to true, sets the Delta_time ΔT equal to the time from the active to the peak, and sets a timer equal to Delta_time before proceeding to step 124. If the peak has not been reached, routine 100 proceeds to step 132.

Returning to step 118, if the peak reached flag is set equal to true, routine 100 proceeds to decision step 124 to determine if the timer has expired and, if not, proceeds to step 126 to update the Delta_time before proceeding to step 132. If the timer has expired, routine 100 proceeds to decision step 128 to determine if the number of active channels equals one and, if not, proceeds to step 132. If the number of channels equals one, routine 100 proceeds to step 130 to activate the switch and sets the switch active equal to I_max_channel. Thereafter, routine 100 proceeds to step 132 to output the switch active signal before ending at step 134.

Accordingly, the adaptive time determination routine advantageously determines an adaptive time for determining activation of the proximity switches. The adaptive time advantageously allows for a user to explore the proximity switch pads which can be particularly useful in an automotive application where driver distraction can be avoided. The adaptive time delay provides for a reduced delay when the user's finger moves fast and an increased delay when the finger moves slower across the switch pads.

It is to be understood that variations and modifications can be made on the aforementioned structure without departing from the concepts of the present invention, and further it is to be understood that such concepts are intended to be covered by the following claims unless these claims by their language expressly state otherwise. 

We claim:
 1. A method for detecting activation of a proximity switch comprising: generating an activation field with a proximity sensor; monitoring a signal responsive to the activation field; generating an adaptive time delay based on a rate of increase of the monitored signal such that a higher rate generates a shorter time delay; detecting a peak amplitude of the signal; and determining activation of the switch after expiration of the time delay following the peak amplitude detection.
 2. The method of claim 1, wherein the step of generating the adaptive time delay comprises determining a time period for the signal to increase from a first threshold to a second threshold.
 3. The method of claim 2, wherein the second threshold comprises the peak amplitude.
 4. The method of claim 2, wherein the adaptive time delay further comprises an additional delay time.
 5. The method of claim 1, wherein the step of determining activation comprises comparing the monitored signal to a threshold and determining activation if the monitored signal exceeds the threshold after the expiration of the time delay.
 6. The method of claim 1, wherein the proximity switch is installed on a vehicle for use by a passenger in the vehicle.
 7. The method of claim 1, wherein the proximity switch comprises a capacitive switch comprising one or more capacitive sensors.
 8. A method for detecting activation of a proximity switch comprising: generating activation fields with a plurality of proximity sensors associated with a plurality of proximity switches; monitoring a signal responsive to each of the activation fields; determining a rate of increase in signal amplitude for each signal; generating an adaptive time delay based on the rate of increase such that a higher rate generates a shorter time delay; detecting a peak amplitude of the signal; and determining activation of one of the proximity switches after expiration of the time delay following the peak amplitude detection.
 9. The method of claim 8, wherein the step of determining activation of one of the proximity switches comprises comparing the monitored signal to a threshold signal and determining activation if the monitored signal exceeds the threshold after the expiration of the time delay.
 10. The method of claim 9, wherein the step of generating the adaptive time comprises determining a time period for the signal to increase from a first threshold to a second threshold.
 11. The method of claim 10, wherein the second threshold comprises the peak amplitude.
 12. The method of claim 8, wherein the adaptive time delay further comprises an additional delay time.
 13. The method of claim 8, wherein the proximity switch is installed on a vehicle for use by a passenger in the vehicle.
 14. The method of claim 8, wherein the proximity switch comprises a capacitive switch comprising one or more capacitive sensors.
 15. A proximity switch assembly comprising: a plurality of proximity switches each providing a sense activation field; and control circuitry processing the activation field of each proximity switch to sense activation, said control circuitry monitoring a signal responsive to the activation field, generating an adaptive time delay based on a rate of increase in signal amplitude such that a higher rate generates a shorter time delay, detecting a peak amplitude of the signal, and determining activation of a switch after expiration of the adaptive time delay following the peak amplitude detection.
 16. The switch assembly of claim 15, wherein the adaptive time delay is generated by a time period for the signal to increase from a first threshold to a second threshold.
 17. The switch assembly of claim 16, wherein the second threshold comprises the peak amplitude.
 18. The switch assembly of claim 15, wherein the step of determining activation of the switch comprises comparing the monitored signal to a threshold and determining activation if the monitored signal exceeds the threshold after the expiration of the time delay.
 19. The switch assembly of claim 15, wherein the plurality of proximity switches are installed in a vehicle for use by a passengers of the vehicle.
 20. The switch assembly of claim 15, wherein the plurality of proximity switches comprise a plurality of capacitive switches each comprising one or more capacitive sensors. 